[BUG] False positive "model retired" warning for claude-sonnet-4.6

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude Code displays a retirement warning for claude-sonnet-4.6, which has not been retired:

Claude Sonnet 4 retired June 15, 2026 · /model to switch

The retirement check appears to match on the shortened display name "Sonnet 4" rather than the full model ID, causing a false positive for claude-sonnet-4.6 users.

What Should Happen?

No retirement warning should appear for claude-sonnet-4.6. The check should match against the exact model ID (e.g., claude-sonnet-4) rather than a display name or partial string, so that point releases like claude-sonnet-4.6 are not incorrectly flagged.

Error Messages/Logs

Claude Sonnet 4 retired June 15, 2026 · /model to switch

Steps to Reproduce

1. Set "model": "claude-sonnet-4.6[1m]" in settings.json (and optionally ANTHROPIC_DEFAULT_SONNET_MODEL=claude-sonnet-4.6[1m])
2. Start a Claude Code session
3. Observe the retirement banner: "Claude Sonnet 4 retired June 15, 2026 · /model to switch"
4. Run /model — it confirms the active model is claude-sonnet-4.6[1m] (not the retired claude-sonnet-4)

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.179

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_